Combined Metalens for Detecting Optical Vortices and Polarization States

A metasurface, including a metalens, in a thin film of amorphous silicon for the visible range is considered. This metasurface enables the simultaneous determination of topological charges –1, 1, –2, and 2 and the direction of rotation of the polarization vector (clockwise or counterclockwise) in an axial superposition of four optical vortices with left- and right-handed circular polarization by measuring the intensity at several specified points at a certain distance from it. The metasurface is composed of two simpler metasurfaces, parts of which are assembled into a combined metasurface in a checkerboard pattern. To form a metalens, a binary zone plate is embedded into the metasurface. The working element of the metasurface (its meta-atom) is a binary subwavelength diffraction grating, the rotation angle of the polarization vector of which depends on the slopes of the lines.